Dependent scattering criterion modification of disordered dispersed particulate medium with the consideration of particle random distribution and high complex refractive index effects

Abstract

Spectral radiative transfer between particles of dispersed particulate medium occurs widely in many fields, where the dependent scattering effect exists. However, most studies use the independent scattering assumption because of the difficulty of dependent scattering calculations. Therefore, the primary task of the radiative property calculation of a dispersed particulate medium is to determine whether independent or dependent scattering is applicable based on the dependent scattering criterion. However, the conventional dependent scattering criterion is proposed 40 years ago, which has three limitations and may cause significant errors: 1) the rhombohedral lattice ordered distribution assumption, 2) ignoring the near-field effect which is composed of multiple scattering between particles, and 3) the optical soft particle with weakly absorption assumption. To overcome the above three limitations of the conventional dependent scattering criterion in radiative transfer studies of dispersed particulate medium, the authors propose the idea of combining the random particle distribution, near-field effect which is composed of multiple scattering between particles, and high complex refractive index effect. A multi-particle averaging clearance (MAC) method is proposed in this study, which is combined with the multiple sphere T-matrix (MSTM) method to obtain a more comprehensive dependent scattering criterion. Compared with the conventional method, the method developed by the authors can decrease the average error between experimental data and calculation data from 43.45% to 4.19%. The dependent scattering criterion range of disordered dispersed particulate medium is effectively extended. In addition, a modified correlation equation for the dependent scattering criterion is developed, and the dependent scattering criterion of disordered dispersed particulate medium is that the clearance-to-wavelength ratio c/λ = 4.4 in the range of particle refractive index from 1.6 to 5 and the range of particle absorption index from 0 to 1.